Draper headers generally include a header frame, an elongate cutter bar along a front edge of the frame including a cutter bar beam which carries a plurality of knife guards for guiding reciprocating movement of a sickle knife across a front edge of the cutter bar. On the header is also mounted a draper assembly including a first and second draper guide roller each arranged at a respective end of the draper assembly spaced apart along the cutter bar with an axis of each roller extending substantially at right angles to the cutter bar, a draper canvas forming a continuous loop of flexible material wrapped around the rollers so as to define a front edge of the canvas adjacent the cutter bar, a rear edge of the canvas spaced rearwardly of the cutter bar, an upper run of the canvas on top of the roller and a lower run of the canvas below the rollers. The cut crop thus falls rearwardly onto the upper run of the canvas and is transported longitudinally of the header. Generally, between the draper rollers there is provided a support plate assembly for the upper run of the draper canvas to prevent sagging.
The header of this type can be used simply for forming a swath in which case the material is carried to a discharge opening of the header and deposited therefrom onto the ground. Headers of this type can also be used for feeding a combine harvester so that the materials are carried to an adapter member positioned at the discharge opening of the header for carrying the materials from the discharge opening into the feeder housing of the combine harvester. Yet further, headers of this type can be used for hay conditioners in which the material from the discharge opening is carried into crushing rolls. It will be appreciated, therefore, that the use of the header is not limited to particular types of agricultural machine but can be used with any such machine in which it is necessary to cut a standing crop and to transport that crop when cut longitudinally of the header for operation thereon.
The draper canvas normally comprises a fabric which is coated with a rubber material which is then vulcanized after forming of the fabric into the required shape and after attachment thereto of transverse slats.
The arrangement shown in U.S Pat. No. 5,459,986 (Talbot) issued Oct. 24 1995 and assigned to the present Assignees of the above patent has achieved significant success and has been used for many years. It provides a seal between an under surface of a rearwardly extending element of the cutter bar and a front edge portion of the upper surface of the canvas.
Not shown in the above patent is the conventional guiding arrangement to prevent misalignment of the draper canvas on the rollers and this is provided by a bead located on the underside of the canvas which runs in a groove in the roller.
An alternative arrangement is shown in U.S. Pat. No. 6,351,931 (Shearer) issued Mar. 5th 2002 also of the present Assignees. This provides an additional guide bead on the outer surface of the canvas which runs in contact with the edge of the element of the cutter bar. This arrangement has not been successful and has not been adopted since it failed to provide the expected improvements over the Talbot arrangement.